Aerators are known which are utilized to increase the oxygen content of water, i.e., to "oxygenate" water, within a body of water. Aerators placed into a body of waste water have heretofore incorporated a draft tube having an open bottom end located at a depth of the waste water to be aerated, and an open top end extending near to the surface of the waste water. The aerator includes a mechanism for drawing water through the open bottom end and displacing the water vertically to mix with air as the water exits the open top end. In some apparatus, the mechanism is a rotary device such as a pump or an impeller while in other apparatus the device is a conduit for injecting pressurized air into the draft tube. The latter device is referred to as an "airlift".
Aerators of both types are disclosed in U.S. Pat. Nos. 3,466,608; 3,972,965; and 3,966,599.
Airlifts operate on the principal of using air to displace water to cause a pumping action of the water. Airlifts have been used to transfer water from one treatment zone to another and have been used in different types of water treatment systems. Airlifts also enhance mixing and oxygen transfer into a waste water stream to aid in the treatment of water and wastewater in aerobic water/waste water treatment processes.
It would be desirable to provide an apparatus which would increase the oxygenation and the oxygen transfer efficiency of an aerator useful in water treatment applications, particularly in waste water treatment processes.
Traditional airlifts, due to their configuration, also tend to allow a certain amount of water to escape the treatment zone without being fully treated. It would be desirable to provide an apparatus which would reduce this tendency.